What if every dev who wants an SMT simply creates his own sidechain. This would allow him to implement all the smart contracts that he needs, and would remove the reliance on hive-engine.
This is basically solution 2 I think.
Think of ethereum, anyone can create tokens with smart contracts. The only thing that makes them interoperable are standards (ERC-20/ERC-721 etc) but in practice anyone can do whatever they want with it and create their tokens how they see fit.
So no need for multiple side chains as we can definitely have that on a single side chain.
Afaik the solution blocktrades is creating is going to be different from what hive engine is doing and will not depend on it so if you are worried about hive engine centralization, worry no more, as they will be two different system :)
Amazing. Thanks for the answer!